Month: October 2015

Jointing

These file holders work well for saws and scrapers. One or two light passes will usually suffice.

Careful sharpening can help avoid the need for jointing the teeth but when the teeth are of an uneven height, the first step in saw sharpening is jointing them even. It is extremely easy to joint the teeth with nothing more than a flat file, but there are scads of saw jointer
file holders on the market. Use an 8″ or 10″ smooth-cut flat file and just run the file lightly along the entire length in one pass.

The shiny flats produced by jointing. They’re different sizes because the teeth were different heights.

With your lamp adjusted properly you should be able to see a small, shiny flat on the top of each tooth. Different tooth heights will make different sizes of flats. If there are any teeth without a flat, take another jointing pass. If there are any teeth missing or much shorter than the others, don’t try to joint all the others to match unless there are many missing in a row (in which case you will have to joint all the way down to them and reshape all the teeth to match). Just leave them for now and subsequent sharpenings will eventually catch up to them as the other teeth are jointed and shaped over time.

Shaping

Skip this step if the teeth on your saw are uniform, properly shaped already and simply in need of sharpening. However, if the teeth are in need of reshaping, get the right file, the prepared alignment guide — that scrap of wood with the hole in it — and clamp the saw tightly in the vise, with the teeth just clear of the vise jaws. Start at the handle end and work toward the toe of the blade. Study the flats on the tops of the teeth that were made when you jointed the saw. The goal is to reshape each tooth, with the proper rake angle, such that the flat disappears — but no more than that.

Hold the file so that it is horizontal (0° slope) front to back and the rake angle guide horizontal side to side.

Assuming you are working from right to left, at each gullet you are filing the face of the right tooth and the back of the left. You need to reduce the flat on the left tooth by half, and, while doing so you will finish shaping the face of the right tooth (whose flat was already reduced by half during filing in the previous gullet.) If one tooth’s flat is larger than average, press harder against it when filing — favor it, or crowd it, slightly — so that all the teeth are filed to the same shape. When you finish here, joint lightly to check your work. If the teeth are still not uniform, do the shape-filing again.

Advance the fleam angle guide as you progress down the blade, filing every other tooth (the ones that are facing away from you). Turn the sawaround and repeat for the rest of the teeth.

Filing

Check your file to be sure it’s still sharp. Filing is the step that actually sharpens each tooth and deserves a sharp file. Assuming the handle of the saw is on the right, and you are working toward the left, find a tooth that is set away from you. Place the file in the gullet to the left of that tooth. You want to file the face of the tooth that’s set away from you (you’ll be filing the back of the tooth to the left, the one that’s facing toward you.) It is the faces of the saw teeth are doing the cutting of the wood and filing them in the same direction that they are set allows the file to chatter less and do a neater job on this more critical surface. The surface of the back of a tooth isn’t as vital to the saw’s performance as the surface of the face, so you want the face to receive the best treatment from the file. Filing requires that you maintain three angles: rake, fleam, and slope. The rake angle guide is the scrap of wood with the file stuck in it. The fleam guide is another scrap with the angle-slot sawed in it that rests over the blade (or an angle guide on the bench behind the vise.) With rip-saws, you probably don’t need a fleam guide because the fleam is 90° and fairly easy to maintain by dead reckoning. The slope angle is the angle of the file relative to the floor. It hasn’t been mentioned yet because it should simply be square to the blade, parallel to the floor. Some saw filers adjust the slope angle in relationship to the fleam angle, but for most common fleam angles it makes little difference in the performance of the saw.

If it seems that all these angles pose something of a juggling act, you’re right. But it only takes a few teeth to get into the rhythm and keep all the balls in the air. Check your setup for all the angles and file a tooth. Don’t be surprised by the noise it makes; that’s the back of the tooth that’s set toward you that’s chattering and screeching. The closer the teeth are to the vise jaws the quieter it will be — to a point. Ear plugs are a good idea. Filing should only require light file strokes because the shape of each tooth was created during the shaping step. The goal here is to remove whichever flat spot may remain, creating a sharp, zero-radius tooth. Skip a tooth — remember, you’re filing every other tooth so that you’re filing in the direction of the set — align your file in the gullet, check your coordinates and file another tooth. slide the fleam guide as needed so that it’s a useful reference. reposition the saw in the vise as needed, too. When you reach the end of the saw, turn it around and start again from the handle end going left to right, flip the fleam guide over so it’s angled the correct way. Remember to reverse the rake guide, too, to file the proper angle on the rest of the teeth.

Setting (after filing)

Some sawyers think it best to set the teeth after all the filing is done. Pete Taran says: The conventional wisdom is to set a saw’s teeth before it is sharpened. I disagree with this approach for several reasons. If a saw is set before it is sharpened, then part of the setis removed when the teeth are filed. It is very difficult to try to figure out how much the set is decreased in filing as it is dependent on many factors such as how sharp the file is, how hard you bear on the tooth with the file, and how uniform the saw teeth are filed. I prefer to set the saw after it has been sharpened. By setting the saw’s teeth after it has been filed, a very uniform set can be achieved, which not only makes the saw cut well, but also makes a very nice finish on the piece being cut. It only takes one or two teeth to be over-set to make the edge of a cut piece of wood ragged and rough.

Mike Wenzloff disagrees: when being set, a tooth will rotate outward at the face. For a rip, it presents the face all wrong. For a cross-cut, the fleam angle changes at the point of the set upwards to the tip of the tooth. One cannot escape this. While reducing the fleam on a cross-cut isn’t too big a deal, the rotation is on a rip. Very little set is removed if the setting is done precisely before the final light filing. It is just a couple light swipes per tooth except on the larger rip profile teeth.

Quite often, the previous setting from the last sharpening is still within specifications and you don’t need to do it again. Because, after shaping and filing, you’ve removed some of the set, why do it before hand? Make a test cut to verify. If the saw cuts well: straight and clean. Ta-da! Go saw something. If it drags or binds, add wax. If it still drags, you need to set the teeth. The set gets a little smaller with each filing but you may be able to file the teeth three or four times before needing to set them again.

If a test cut wanders off line, the teeth on the side that the saw is cutting toward are set too much. Use a fine stone on the side with too much set and gently hone those teeth a bit. Lay the saw flat and run the stone flat on the side of the blade to hone down the teeth on that side. Take one or two passes with the stone, test again and repeat if necessary. If the saw cut is difficult to control or wobbles around in the kerf, you may have too much set altogether. Measure it with the above specs in mind and if you find you need to reduce it, try clamping the teeth in a vise with smooth, metal jaws and squeezing them to reduce the
set. Squeeze a vise-worth section, advance the blade, squeeze again trying to use the same amount of pressure, advance the blade, etc. Check the cut, hone or reset as needed. Kevin Drake adds: I much prefer re-setting over honing here, mostly because it has workedfor me when honing has just made matters worse. Besides that, set diminishes with useso just re-setting may make a saw behave as if it has been recently sharpened.

Be sure to coat those freshly cut teeth with rust preventative. You’re done!

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It only requires a few specialized tools and some practice to sharpen a saw.

Tools

A simple saw vice can be made from a couple of solid- or plywood boards 8″ to 10″ and up to the length of the saw. Hinges keep it aligned; leather or rubber jaw liners help with “grip” anddampen some of the noise generated by filing.

Saw Vise

To sharpen a saw, you need a way to hold it securely while you’re filing it. “Official” saw vises are available at second-hand sources (or this great new one from Gramercy) but it’s very easy to make a superior one from a scrap or two of plywood. And, you can make a saw vise that’s closer to the length of your saw than commercial ones, which will save you time re-positioning the saw as you’re working on it. Be sure to have good lighting available. One or two easily adjusted, swing-arm lamps are perfect for the task.

Saw set

A typical saw set. I’ve colored the plunger red for visibility in this photo.It’s easy to set teeth too much. The dial on the saw set should be used as a rough guide, so use caution and calipers to check the set.

Saw sets are readily available and affordable, both new and used. The basic “pistol-grip” style works well. As you squeeze the handle, a small steel plunger pushes against an adjustable, beveled anvil. Some saw sets have a rotating disc with a ramp that’s beveled such that as you turn the adjuster, a different part of the ramp is presented to act as the anvil, modifying the amount of set that the tool will perform with each squeeze. Others have a sliding beveled anvil that is adjusted up and down to dial in the amount of set. The teeth are set in the same direction that they were set previously. Setting a tooth the wrong way — bending it all the way to the other side — can weaken it or even break it off. Take care to match the set direction. The saw set is positioned over the saw blade, a suitable tooth is located, the handle squeezed and the plunger pushes the tooth against the anvil,
bending it the right amount (more later).

Files

The simple guide on the end of the file offers a visual reference to keep the file cutting the proper rake angle on each tooth. The fleam guide, the parallelogram with a slot pictured here on the bench gives a similar reference when filing cross-cut teeth that need an angled bevel. You simply hold your file parallel to the fleam guide as it sits over the saw blade.

The simple guide on the end of the file offers a visual reference to keep the file cutting the proper rake angle on each tooth. The fleam guide, the parallelogram with a slot pictured here on the bench gives a similar reference when filing cross-cut teeth that need an angled bevel. You simply hold your file parallel to the fleam guide as it sits over the saw blade.

You’ll need an 8″ or 10″ smooth-cut flat file for jointing and a small triangular file for tooth shaping and filing. There is plenty of advice available about triangular file sizes, but Mike Wenzloff of Wenzloff and Sons says to use the smallest file that will fully
file the back of the next tooth. A smaller file has a sharper corner and will cut the gullet — the concavity between teeth — deeper for better chip clearance. He also tells me that he can sharpen over twenty saws with a file before the file wears out.

Always use a file handle. The control required, and the comfort you deserve, make this mandatory. Also, those small triangular files have tangs that will hurt you if left unhandled. You can make a handle easily enough but they’re inexpensive to buy and reusable. Filing is usually a two handed job so some sort of “handle” on the other end of the file is a good idea. This outboard handle can be a simple scrap of wood with a hole drilled all the way through to receive the file. The hole should be small enough that the file can be lightly driven in. This additional handle will act as a guide to keep the file rotated to file the proper rake angle in the teeth. To make it easier to reuse this rake angle guide, you may want to mark the rake angle on both sides and to identify which side the handle of
the saw is on so you can line everything up next time you use it.

Speaking of guides, a fleam or bevel-angle guide is handy for filing cross-cut saws. You can lay a bevel gauge set for the correct angle on the bench behind the saw vise or cut a slot in a scrap of wood (both sides) that you slip over the teeth near where you are filing. Either will serve as a visual aid and help keep your file at the proper angle.

Setting (before jointing)

Setting saw teeth before jointing assures that the tops of the teeth will all cut in the same plane. If you set after filing, your flat-topped, jointed teeth will be bent slightly outwards. And, those flat-tops will be bent out of plane with each other. Because professional saw sharpeners debate whether to set before or after sharpening, it seems to me to be a matter of personal preference. As your experience with saw sharpening grows, the difference(s) should become more obvious and you’ll probably end up in one camp or the other. To set the teeth, you can clamp the blade in the saw vise such that the teeth are enough above the jaws to allow comfortable access with the saw set. As sawmaker Kevin Drake says: “I find it more comfortable to just hold the saw in my left hand and set the teeth with my right. My hands sort of wiggle down the saw as this happens.” Sawmaker Mike Wenzloff adds: “holding a saw in one’s lap works with smaller back saws. Not so well on 28″ 4 tpi rips.”

Begin setting with the teeth closest to the handle. Because those teeth get far less use you can use them to fine tune your settings. Adjust your saw set according to the manufacturer’s instructions. often the anvil adjustment is based on a scale of teeth per inch, but when it comes to any one saw, this may not be accurate. And some saw-set scales are just arbitrary reference numbers. Start with a setting that corresponds to more teeth per inch than your saw actually has. That should make for a smaller amount of set; a good
place to start as the saw set’s settings aren’t the code, they’re more what you’d call guidelines than actual rules. Select a tooth that’s set away from you and position the saw set over it with the plunger pointing at the tip of the tooth. Squeeze the handle to set the tooth. Move the saw set over, skip a tooth, and set the next one that’s going away from you. Do a couple more, applying pressure evenly with each tooth, turn the saw around and set the teeth you jumped over in that same section so that you have an inch or so of set teeth. Now measure. Compare the width of the blade stock to the overall width of the teeth you just set. The set of the teeth should increase the thickness of the blade by about 20% for dry hardwoods; up to 30% for soft- and green woods.Example: A saw blade with a thickness of 0.035″ (0.9mm) should be set to a width of 0.042″ (1.1mm) for hardwoods and 0.045″ (1.2mm) for softwoods. Notice how little set there really is: the total thickness is increased by only .007″ (.18mm) to .010″ (.25mm) so any one tooth is set just .0035″ (0.09mm) to .005″ (.13mm) — that’s only three and a half to five thousandths of an inch. That’s not very much, and because it is easier to add more set than it is to remove, use care not to over do it. After measuring and subtracting, adjust your setting procedure to accommodate the new data and continue to set the saw.

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I’ve fielded a few questions lately about saw sharpening (obviously from woodworkers who haven’t yet read my book on sharpening for woodworkers) and thought this would be a good time to give away (most of) a sample chapter. I hope you enjoy it and that it helps you to keep your saws in optimum condition. — Ron

A saw is a long row of small chisels – sort of. It helps if I keep that image in mind when
I think about sharpening one. But the row-of-chisels analogy is only so good; my imagining must also include the set of the teeth. As the row of chisels cuts through the wood, the rest of the saw, the flat blade that the teeth are part of, follows along through the
cut. The path through the wood, the gap or slit, created by the teeth is the kerf, and if the kerf is the same width as the saw blade, the saw will rub, drag and bind during cutting, making the cut difficult if not impossible to finish. To solve this problem, the teeth of a saw are set by bending them slightly outward, one tooth bends one way, the next tooth the other way and so on along the edge of the saw, so that they cut a wider kerf and allow the rest of the blade to travel unimpeded. Bending the teeth is possible because saws are usually hardened to a mid range hardness — hard enough to hold an edge for sawing but still soft enough to set and to sharpen with a file.

Unfortunately, my “row of chisels” image does not take into account the fact that most saw teeth are sharpened to a negative rake angle and actually cut more like scrapers than chisels. My powers to visualize reach only so far.A saw tooth’s singular purpose is to remove wood. While a chisel or a plane iron may be called on to do the same thing, we often demand that they leave behind a fine, smooth surface at the same time. To ensure that fine surface, we hone and polish the edges on plane irons, chisels, carving tools, anything that we use to create a smooth surface. Though all the woodcutting edge geometry applies, saw teeth are sharpened to achieve a different goal: they must simply remove material efficiently. A smooth, finely honed, polished cutting edge is not called for; therefore we sharpen saws with a file — an efficient tool to do an efficient job of making an efficient tooth.

Some contemporary saws have induction hardened teeth that can’t be sharpened or re-set; they’re too hard for filing or bending. You can tell induction hardened teeth by the rainbow discoloration at the toothline. These saws will tend to stay sharp for a long time but when one is finally dull, you will have to replace it. Being able to file a saw yourself isn’t only about keeping it sharp. You can also modify the shape of the teeth for different cutting situations. A saw’s edge geometry can be adjusted for optimum performance in, say, green softwoods, which require more set compared to dry hardwoods.

There are two fundamentally different sawing tasks: ripping and crosscutting. Ripping is cutting more or less in the same direction as the grain runs in the wood (with-the-grain) while cross-cutting, as the name implies, is cutting across the grain (cross-grain, see Chapter Four: How Wood is Cut). A rip saw is usually used to narrow a board while a cross-cut saw usually shortens one. Each cutting action calls for a different cutting edge geometry. A cross-cut saw is used for almost any angle of cross-cutting, whereas rip-sawing is most commonly used to cut close to parallel with the grain.

Tooth geometry of a typical rip saw.

Ripping is done with teeth that resemble square-edged chisels held at a near-vertical scraping angle. Each tooth makes a small, curly shaving much like a small version of the shaving made during with-grain planing. Rip saw teeth are usually filed with a rake angle between an aggressive 0° and a more laid-back 15°. The larger rake angle makes it easier to start a cut; the more vertical teeth will cut faster. Pete Taran (www.vintagesaws.com) suggests a 4° rake as a good compromise for rip saws.

Tooth geometry of a typical cross-cut saw.

Cross-cutting wood fibers requires some special cutting action. The end-grain fibers that line the kerf must be severed then rolled up and out of the path of the blade. So, to facilitate cross-cut sawing we add an angle to the tooth of the saw in order for it to achieve the fiber-severing goal, allowing a clean cut that leaves a relatively smooth surface along the sides of the kerf. This angle on cross-cut teeth is called fleam, which is also the old-fashioned term for the lancet used to open a vein for bloodletting. Fleam is an angle on the face of the tooth (and generally on the back as well) much like a skew chisel, compared to a rip tooth’s similarity to a square-edged chisel. The sharp point of the skew cuts deeper than the rest of the tooth in order to sever the wood fibers along the sides of the cut, while the rest of the tooth cleans out the kerf.

Rip-saw teeth are filed straight across, the file held at 90° to the saw blade. Cross-cut teeth are filed at an angle from 10° to 45° with 15° being popular for a general-purpose cross-cut saw. Cross-cut teeth have a less aggressive, negative rake angle of 12° for a fast, aggressive cut, to 30°, which is more typical and gives a smoother though slower cut. Another aspect of saw tooth geometry is slope, which refers to the angle of the file from horizontal.

Though it may seem a daunting task (all those teeth!) you can sharpen your saw yourself. Most power-saw blades are either carbide, which is sent to a specialized shop for sharpening, or disposable and simply replaced with new blades when dull. Keep in mind, though, that a good hand saw is another of the many hand tools that will last for generations if cared for and kept sharp. There’s nothing difficult about filing a saw; like everything else it’s a skill to learn and with a small amount of practice, you can make your
saw work better than it did new — a finely tuned tool that you’ll find myriad uses for.

These days, much of your sawing tasks are likely done with one of the power saws that we all seem to have, but there will always be a place for hand saws and hand sawing in any fine-woodworker’s tool kit, and skill set. As your saw sharpening skills improve, you’ll find yourself sharpening your saw more often because you are using it more often, and vice versa. A hand saw is frequently your best tool for many sawing tasks. When you keep your hand saw in good fettle, you’re likely to find yourself turning your back on the noise, dust and danger of power saws in favor of your uncle’s classic, well-tuned Disston (et al), or
one of the beautiful new-generation of saws being produced today.

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The Perfect Edge

"... makes his new book 'The Perfect Edge' one that should not only be read cover to cover (multiple times), but owned and consulted regularly by any woodworker who is serious about his craft, and/or works with edged tools and/or likes their tools working at an optimum level... The book is beautifully presented, and absolutely jam-packed with well presented information... This is the bible on sharpening... If you but remember a fraction of this book, and put it into practice, your tools will be deadly sharp, and a pleasure to use." -- Stuart Lees